Hey i was wonderin for my school project, does oil have the ability to preserve food?

Yes, oil potentially has the ability to preserve food, but this must be carefully done. Oil is used in preservation by creating a (mostly) oxygen free environment if the object to be preserved is fully submerged in the oil. However, some bacteria and spores can survive (and even thrive) in an oxygen deficient environment. Only attempt to preserve food if you are experienced in this or are learning to do it from someone who is experienced.

I'm not sure why anyone would want to A) Deep fry at a temperature higher than 375 degrees, and Saute at a temperature higher than about 300 degrees. So, why would one need grapeseed oil for its high smoke point? (I use it because it has a clean, neutral flavor and a light viscosity.)

I'm not sure why anyone would want to A) Deep fry at a temperature higher than 375 degrees, and Saute at a temperature higher than about 300 degrees. So, why would one need grapeseed oil for its high smoke point? (I use it because it has a clean, neutral flavor and a light viscosity.)

Michael, trans fats are made through the process of hydrogenation. While heating an oil past its smoke point will cause it to break down and oxidize, it DOES NOT cause trans fats. Definately *avoid* shortening and partially hydrogenated vegetable oils! It's a good idea not to cook any oil under high heat circumstances.

true, high high on unstable oils creates lipid peroxides, which are also unhealthy.

I disagree they are not impurities, they are associated cofactors/enzymes that I consider as nutrients.
We learned in chemistry that oils can quicky go rancid if left in the light (photoreactive) as well as oxidize. Isn't it interesting that most oils at the store are in clear bottles that have a shelf life of 2 to 3 years if not longer, whereas their counter parts unrefined oils will decompose and go bad within months.
Why is that I believe it is because of the refining process, oils put under high temperatures and all "impurities as you put it" have been removed. Thus increasing shelf life so the store owners don't have to throw it away.

This same mentality has been used with Milk and Eggs, does anyone remember how Milk used to only last a week before curdling. Now it lasts twice as long. Remember when we used to crack eggs and sometimes would find alittle white thing in there along with some blood, not anymore what happened how come? eggs used to go bad in our fridge within 2 weeks, that was fun because we used to get them to have an egg war. Unfortunately not anymore, Im older now but Ive had eggs in the fridge for 3 weeks and after opening them they looked fine why is that?

sorry for the long statement, main point is that oil reacts to light but not any of the oils at the store why?

Over here, milk lasts longer than it used to because of the advances in pasteurisation. This (as I understand it) is treating the milk to kill any bacteria in it that cause it to go bad. This lengthens shelf life by a huge amount, although once the milk is opened, it will go off eventually due to bacteria "migrating" into the bottle. If you want an even longer shelf life, then you can buy UHT (Ultra High Temperature) milk, which is essentially boiled at high temperatures to kill virtually all bacteria.

Eggs no longer have those spots in them because they are unfertilised. This means that there is no chance of getting chicken embryos in the eggs. Our eggs are also lion-marked, meaning that the chickens that leyed them were vaccinated against Salmonella.

It's interesting that you pointed out *exactly* what's so convenient and disturbing about current food processing. People want milk that looks the same throughout (i.e. not with cream on top and separation of fat particles) and that lasts longer than a few days. We also want eggs that don't look like little embryos. We especially don't want to risk getting sick from our food and so many of our foods today are irradiated, homogenised, pasteurised, sterilised and so on.

Brigning it back to oils, the question of why oils last so long on the shelf is a good one. And why doesn't canola oil smell like....anything? The refining process requires a lot of mechanical pressure and heat and the oils simply oxidise. Then they have to bleach and filter them to get them to look the way they do in those clear bottles on the shelf. If you can find Rapunzel oils in your local health food stores, you should splurge sometime on a bottle of their organic, unrefined canola oil. It's a rich yellow colour and has the most amazing smell and taste. I love to bake cookies with them (being sure to keep the oven below 300F) yum!

But of course, the smoke point is then so much lower with unrefined oils. I try to do the olive oil/coconut oil combo when I need to stir-fry, and then I drizzle on sesame oil at the end just for flavour.

A friend of mine and myself were having a fairly heated (haha geddit!) argument the other night (albeit after a few beers) over whether sunflower oil or olive oil burns at a higher temperature... I said sunflower oil burns hotter, and so is better for things like stir frys, sauteeing etc... I think this shows I was right, although we didnt specify the exact conditions... Going with the unrefined values... I win!

Remember when we used to crack eggs and sometimes would find alittle white thing in there along with some blood, not anymore what happened how come? eggs used to go bad in our fridge within 2 weeks, that was fun because we used to get them to have an egg war. Unfortunately not anymore, Im older now but Ive had eggs in the fridge for 3 weeks and after opening them they looked fine why is that?

This is actually all wrong. I (well actually my wife) produce eggs for the local farmer's market. We don't do _anything_ to our chickens, just give them food and water and shelter, and steal their children.

The eggs we sell do occasionally have blood or meat spots. Commercial eggs don't have those because they are "candled". This originally meant that someone literally held each egg up to a candle, looking for any weird shadows that indicated something not quite right. Modern egg production uses machinery, including a contraption that rolls eggs past some sort of optical electrosensor. This is also the main reason that white eggs are so popular in the US: they're much easier to candle (which means the producer would rather deal with them) and the candling results are more certain (which means the consumer is happier with them).

We rarely get complaints about blood or meat spots, nor do we often find them in the eggs we eat. I believe this is because our chickens are healthy and active. Meat spots are literally bits of chicken meat -- bits of the hen that broke off and got incorporated into the egg while it was being produced. Imagine something similar to the colon polyps we're all told to watch out for. Blood spots are likewise bits of blood that leaked in during production. These things can happen as part of normal wear and tear in the bird. But imagine birds that live in 1x1 foot cages where they can barely turn around, fed high-energy feed full of hormones and god knows what else (probably not antibiotics -- I think that's actually illegal in the US, even for the big commercial operations). Birds that aren't healthy or physically fit. I imagine these birds probably make more blood & meat spots than ours. I have no specific facts to back this up, just the observation that we seem to have very few spots in our production. Not enough to warrant the effort of candling.

The only machine we use is a compressor to bubble air into an egg bath. We "wash" our eggs in dilute baking soda (sodium bicarbonate) solution.

Our eggs are fertilized (roosters run with the hens). We label them as such: "fertilized", not "fertile". We refrigerate our eggs (ok, I was wrong, that's a 2nd machine. The car we drive them to market in is as third.) Refrigerated eggs can sometimes be hatched, but they are not reliably fertile. If someone wants eggs for hatching, we make special arrangements to bring them un-refrigerated eggs. We are careful to label "fertilized" because this matters to certain subspecies of vegetarians.

Our eggs never look like embryos because bird eggs do not begin to develop until they have been held consistently warm for about 48 hours. This is a natural mechanism to prevent a nest full of eggs from hatching one by one (which results in mama hen wandering off to care for the first hatchling, and the rest of the eggs dying of cold). Mama bird lays an egg, sits on it for an hour or so, wanders off to eat, has a normal day. That night she sits on the eggs and keeps them warm all night. Repeat the next 6-10 days. Eventually there are enough eggs, she decides to seriously sit. That first egg has been sat on (brought up to body temperature) many times, possibly 10 times for 8-12 hours each time, but it has not progressed any farther in development than the last one laid. All the eggs in this nest will develop at the same rate and hatch within 12-24 hours of each other (21 days later, for chicken eggs).

Eggs do not go bad in 14 days in the fridge. Eggs don't go bad in 14 days on the counter, even a sunny counter. Before we started selling at the market, we often ate our own eggs that had been refrigerated for five months. By then they were starting to get runny, but still perfectly edible. If your mom gave you the eggs after 14 days, it was because she believed they were too old, not because they were actually going bad.

The USDA currently requires eggs to be labeled with their pack date and an expiration date 30 days later. Note that it is the pack date (which could be arbitrarily later), not their lay date. We label with the lay date, which is technically in violation, but always earlier or the same as the pack date (so at worst we are making our eggs "seem" older than they are, by their standards).

It may be that the USDA (equivalent agency back then?) used to require a 14-day expiration stamp. So your mom believed it and gave you eggs to throw. Now you're in charge of the fridge and you believe the 30 days stamped by today's standards.

Note that you cannot reliably expect store-bought eggs to last for 5 months in the fridge. Because the USDA has producers label by pack date, you really have no idea how old your eggs are. There's actually a reason that producers might deliberately age eggs: truly fresh eggs don't hard boil well. Well, they boil just fine, but they're really hard to peel. Bits of egg white stick firmly to the shell; you end up shredding the white pretty badly. If one brand of eggs had that property and the next one didn't, which one would still be on the market 6 months later? So there's a strong incentive for egg producers to age their eggs a few weeks, despite the inventory management costs. Once you have the necessary warehouse space to handle this rotating inventory stream, the exact age of eggs making it to store shelves is going to ebb and flow according to how the chickens are producing and how many eggs people are buying.

We don't do anything specific to combat this. If a customer mentions they intend to hard-boil, we steer them to an older dozen (we go to market every 1-2 weeks, so we have eggs at least a week old). We tell them to save the eggs a couple weeks before using them for that purpose. And we tell about a couple tricks: lightly crack the egg before boiling (it will leak a bit but may be easier to peel); themally shock them after boiling (drop into cold water until cool, drop back into the still-hot boiling pan). We haven't actually experimented enough with these techniques ourselves, we just use old eggs for hard boiling.

Michael, trans fats are made through the process of hydrogenation. While heating an oil past its smoke point will cause it to break down and oxidize, it DOES NOT cause trans fats.

Oh yes it does!

Here's the chemistry. "trans" and "cis" refer to the shape of otherwise identical molecules. In an unsaturated fat, there are occasional double bonds. This leaves two adjacent carbon atoms with only a single hydrogen attached to each instead of the usual two. This produces a slight push on one side of the chain. Hence the molecule can take either of two shapes: if the hydrogens are on the same side, the chain gets a (double) kink, if they are opposite, there is just a tiny zig-zag and the chain remains pretty well straight.

The natural form of most fats is the kinked "cis" isomer, the straighter "trans" form is unnatural and harmful. Both forms are stable at room temperature. However, when oil is heated the thermal vibration can wrench the double bond around into the other position. This occurs below the smoke point, so high temperature cooking transforms some of the natural cis fat into the harmful trans variety. It is not entirely negligible - this is one of the reasons they recommend not using cooking oil over and over again.

One more off-subject comments on the eggs -- I also have had chickens and raised my own eggs, and one of the first things I noticed was how much thicker the shells were on my home grown eggs.

Here is my hypothesis -- grocery store eggs come from chickens fed the bare minimum to get the product to market and maximize profitability. Thin shells are the result of less availability of minerals in the chicken's system to produce a thicker shell. Thin shells also allow the eggs to be "candled" or optically inspected more efficiently (for all of us consumers that value predictability in our egg cracking experience). Thin shells also allow oxidation of the eggs (the process that causes spoilage as evidenced by that little bubble of air you find between the membrane and the shell in older eggs, and allows you to do the "float test" to determine an egg's freshness before you are unpleasantly surprised). So, grocery store eggs spoil faster IMHO, and are less nutritious (because that same programming principle of garbage in -- garbage out also works for food processing)

Am I far off the mark, anyone with more knowledge and less experience in this area?